[0001] The object of the present invention is a method of controlling a braking function
of an elevator as defined in the preamble of claim 1.
[0002] It is very general to use a machinery brake that mechanically connects with a rotating
part of the elevator machine as a braking apparatus of an elevator car. The machinery
brake can be in its structure e.g. a drum brake or a disc brake. The braking function
of a machinery brake is conventionally activated by disconnecting the electricity
supply circuit of the brake control winding, e.g. with a relay or contactor. After
the electricity supply of the brake has been disconnected the brake closes, in which
case brake pad attached to the brake shoe connects mechanically with a rotating part
of the machine. The closing of the brake occurs with a closing delay, which is determined
from the electrical parameters of the brake and of a possible attenuation circuit,
such as from the inductance and resistance of the brake, as well as from the impedance
of the possible attenuation circuit.
[0003] The force exerted by a brake is generally quite large, so that when activating the
braking function e.g. in connection with an emergency stop, the brake pad engages
to brake the movement of the elevator car with the kind of deceleration of movement
that might feel uncomfortable to a passenger in the elevator car.
[0004] Rather a lot of kinetic energy is also generated when the brake operates. This produces
a loud noise when the brake pad hits against the braking surface. To solve this problem
the aim has been for the distance between the brake pad and the braking surface to
be as small as possible. In this case the brake pad does not have time to achieve
a very great speed and kinetic energy when it hits closed, as a result of which the
impact is more subdued. An air gap that is small enough is, however, difficult to
implement and also to adjust, and this type of solution results in a very fragile
structure and also in extremely precise manufacturing tolerances.
[0005] The operation of a brake of an elevator can be affected also by adjusting the current
of the brake. Publication
JP 2008120521 presents one such type of adjustment of the brake current wherein the braking force
is measured from the brake drum with a special pressure sensor, and the current of
the excitation winding of the brake is adjusted on the basis of the measuring signal
of the pressure sensor. In this case the braking force can be affected with the adjustment
of the brake current. A way of reducing the braking force is also shown in document
EP 1 980 519 A1 according to which a resistor diminishes the current flowing through the braking
coil.
[0006] Publication
JP 2008120469 presents an arrangement wherein it is endeavored to reduce the noise produced by
the operation of a brake by changing the impedance of the electricity supply circuit
of the brake in stages such that the change in impedance also affects the magnitude
of the brake current.
[0007] The aim of this invention is to solve the aforementioned drawbacks as well as the
drawbacks disclosed in the description of the invention below. In this case a brake
control method of an elevator is presented as an invention, the brake control circuit
of which is simpler than in prior art. By means of the brake control circuit the operation
of a brake of an elevator can be controlled so that the level of operation of the
elevator system is improved. In this case by means of the brake control circuit a
safer and more pleasant user experience from the viewpoint of an elevator passenger
can be achieved, particularly in an emergency stop of the elevator.
[0008] The brake control method according to the invention is characterized by what is disclosed
in the characterization part of claim 1.
[0009] Some embodiments are also discussed in the descriptive section of the present application.
[0010] The brake control circuit comprises a first switch that controls the electricity
supply of the winding of the brake, which switch is switched in a controlled manner
with short pulses by the control of the electricity supply of the winding of the brake,
and thus the braking function is controlled. In this case e.g. the voltage between
the poles of the winding of the brake and/or the current flowing through the winding
can be adjusted according to a predefined reference. Since the instantaneous current
of the winding affects the instantaneous value of the force exerted on the brake shoe,
the force exerted on the brake shoe can in this way be adjusted according to the objective
of the operation of the elevator at any given time. The current profile of the winding
of the brake can be selected e.g. so that the impact caused by the opening movement
or closing movement of the brake is moderated. On the other hand, during an emergency
stop of the elevator the movement of the elevator car can be adjusted, on certain
conditions, by controlling the current flowing through the winding of the brake and
thus the braking force.
[0011] According to the invention, after the electricity supply of the winding of the brake
has been disconnected, the energy stored in the winding is discharged into an intermediate
circuit of the brake control circuit via a release branch. In this case the magnetization
energy stored in the winding of the brake can be collected. At the same time also
the conventional attenuation circuit of the current of the brake, in which the magnetization
energy of the winding of the brake is converted into heat, can be omitted or the dimensioning
of it can at least be reduced.
[0012] In one embodiment of the invention, when the voltage of the intermediate circuit
exceeds a set limit value, energy is discharged into the attenuation circuit fitted
in parallel with the winding of the brake. In this case the attenuation circuit functions
as an overvoltage protector of the winding of the brake.
[0013] Still according to the invention a capacitor is connected between the rails that
transfer output current and return current to the intermediate circuit of the brake
control circuit. The capacitor in this case functions as an energy store, in which
the energy returning to the intermediate circuit from the winding of the brake is
stored. The energy stored in the capacitor can also then be re-used as magnetization
energy of the winding of the brake. If the intermediate circuit is made to be unregulated,
e.g. by rectifying the voltage of the AC voltage source with a diode rectifier, the
variation of intermediate circuit voltage can also be compensated with the capacitor.
[0014] In one embodiment of the invention the current of the brake is adjusted towards the
set reference for brake current by switching the first controllable switch with short
pulses.
[0015] In one embodiment of the invention a first controllable switch is fitted in series
with the winding of the brake, which switch is switched with short pulses, for controlling
the electricity supply of the winding of the brake. A second controllable switch,
which when controlling the brake is kept continuously closed at the same time as the
first controllable switch is switched with short pulses, is further fitted in series
with a winding of the brake. The electricity supply from the intermediate circuit
to the winding of the brake is arranged to be disconnected by opening the second controllable
switch. Since the second switch is continuously closed when current is flowing, no
switching losses whatsoever occur in the switch, but instead only transmission losses,
and therefore a switch that is dimensioned for smaller dissipation power can be used
as a switch. In this case also a mechanical switch, such as a relay or a contactor,
can be used as the second switch.
[0016] In one embodiment of the invention a first and a second switch are arranged to be
controlled on the basis of the status data of the safety circuit of the elevator.
In this case, when an operational nonconformance of the elevator system so requires
it, the first and the second switch can be controlled open, in which case the brake
closes immediately; on the other hand, the brake-opening and/or brake-closing force
can also be controlled by supplying current to the winding of the brake, if the detected
operational nonconformance does not require immediate disconnection of the control
of the brake. The safety circuit of the elevator can be formed of e.g. a safety circuit
of an elevator that is, in itself prior art, with the safety contacts incorporated
in said prior-art safety circuit. The safety circuit can also be implemented using
an electronic monitoring unit, which is made from prior-art electronic safety devices
complying with the required design criteria. The monitoring unit can in this case
comprise e.g. a duplicated processor control, which is in connection with the sensors
that measure the safety of the elevator as well as with the actuators that perform
the procedures ensuring safety of the elevator via a communications channel between
them. In this case the monitoring unit determines the status, i.e. operational state,
of the elevator system on the basis of the measurement data of the safety sensors.
A sensor that measures safety can be e.g. one of the following: a safety switch of
a landing door of the elevator, a final limit switch of the elevator, a safety switch
that is temporarily activated and that determines a temporary safety space at the
top end and/or at the bottom end of the elevator hoistway, and also a monitoring unit
of the overspeed of the elevator/overspeed governor safety switch; the sensor can
also be, for instance, an electronic sensor, such as a proximity sensor, corresponding
to one of the aforementioned safety switches. The actuator performing the procedures
that ensure the safety of the elevator can be e.g. the brake control circuit of the
machinery brake, and also the control circuit of the gripping apparatus of the elevator
car.
[0017] In one embodiment of the invention when detecting a line-to-earth short-circuit of
the brake, only the first switch is closed, and the line-to-earth short-circuit is
in this case determined on the basis of the current flowing through the first switch.
In this case if there is a line-to-earth short-circuit in the winding of the brake,
current starts to flow through the first switch after the switch closes.
[0018] The elevator system comprises a movement control system, which adjusts the movement
of the elevator car according to a set movement reference. The elevator system comprises
a brake control circuit, which brake control circuit comprises a first switch that
controls the electricity supply of the winding of the brake, which switch is switched
in a controlled manner with short pulses by the control of the electricity supply
of the winding of the brake, and thus the braking function is controlled. Movement
control system refers in this context to those devices and softwares that perform
the regulating function of the movement of the elevator car. These include at least
one of the following: the sensors that determine the position and/or movement of the
elevator car and/or the elevator machine and interfaces of said sensors, the position
determining apparatuses of the elevator car fitted in connection with the floor levels
and interfaces of said apparatuses, and also the regulating circuit of movement of
the elevator car and softwares of said circuit.
[0019] In one embodiment the safety circuit of the elevator checks in connection with an
emergency stop the operating condition of the movement control system. The operating
condition of sensors that determine movement of the elevator car can be checked by
comparing the congruity of the measuring data of at least two different sensors. If
the measuring data differ from each other by more than the set limit value, it can
thus be deduced that the movement control system has failed. Malfunctioning of the
movement control system can also be determined e.g. when the position determination
of the elevator car does not succeed; malfunctioning can also be determined if the
movement of the elevator car, such as the measured run-time speed and/or acceleration
of the elevator car, or e.g. the measured speed and/or deceleration of the elevator
car during an emergency stop differs from its set reference value by more than the
limit value for the maximum permitted deviation. Generally the safety circuit in this
case at the same time disconnects the electricity supply of the elevator motor.
[0020] In one embodiment when an operational nonconformance of the movement control system
is detected, the safety circuit disconnects the electricity supply to the winding
of the brake by opening a first and a second controllable switch. In this case the
electricity supply to the winding quickly ceases completely, in which case also the
brake shoe presses against a moving part of the elevator machine with as great a force
as possible, and the brake closes with as short delay as possible. Although the deceleration
exerted in this case on an elevator passenger may indeed feel uncomfortable, this
type of control of the brake is advantageous in situations determined by the safety
circuit of the elevator, such as when the elevator car is situated nearer to the end
of the elevator hoistway than the set limit value, or when detecting an operational
nonconformance of the movement control system of the elevator, such as a fault situation.
The aforementioned type of brake control can be used also e.g. in a situation in which
an overload has been loaded into the elevator car.
[0021] In one embodiment when the movement control system is detected to be in working order,
the safety circuit permits electricity supply to the winding of the brake with the
control of the first and the second controllable switch, and the movement control
system in this case regulates by means of the brake control circuit the movement of
the elevator car during an emergency stop by adjusting the current of the winding
of the brake and thus the braking force of the brake of the elevator so that the movement
of the elevator car approaches the reference set for movement. In this case movement,
such as the speed and/or deceleration and/or position, of the elevator car during
an emergency stop can thus be adjusted in a controlled manner, in which case an emergency
stop is more comfortable from the viewpoint of an elevator passenger.
[0022] In one embodiment the motor control unit of the elevator comprises a non-volatile
memory, in which the parameters of the brake are stored, at least one of which parameters
is the reference for the brake current and also the limit value for the voltage of
the winding of the brake that corresponds to this, and the aforementioned parameters
are transferred from the motor control unit to the brake control circuit via the communications
channel made between these. The aforementioned parameters of the brake can in this
case if necessary be stored in the non-volatile memory of the control card of the
motor control unit, such as e.g. of the frequency converter, already in conjunction
with manufacturing or delivery, in which case parameterization of the brake control
circuit is simplified. Since the machinery brake is normally installed in the hoisting
machine already before delivery of the hoisting machine, the parameters of the winding
of the brake can thus be fitted in conjunction with the own machinery-specific parameters
of the motor control unit, which facilitates installation and commissioning of a hoisting
machine. It is also possible that the motor control unit learns the necessary parameters
of the hoisting machine only in the installation phase, e.g. by injecting voltage
signals and/or current signals into the winding of the motor, and selecting from the
table stored in the memory the parameters of the brake corresponding to the learned
machine parameters.
[0023] In one embodiment the voltage of the winding of the brake is limited to the limit
value for the voltage of the winding of the brake at any given time with the control
of the first controllable switch. In this case the brake control circuit comprises
a regulating loop, in which the brake is controlled by adjusting the voltage between
the poles of the winding of the brake and/or the current flowing through the winding
by switching the first controllable switch with short pulses. The regulating loop
also comprises a measuring feedback for the current between the poles of the brake
and/or the current flowing through the brake, and thus the voltage between the poles
of the winding of the brake is limited to its set limit value by means of the aforementioned
measuring feedback.
[0024] One elevator system comprises at least two brakes of the elevator, both of which
brake a moving part of the same elevator machine. In one embodiment the electricity
supply to the winding of the first brake is in this case controlled by switching the
first controllable switch with short pulses. A third controllable switch is further
fitted to the brake control circuit, which switch is fitted in series with the winding
of the second brake, and the electricity supply to the winding of the second brake
is controlled by switching the aforementioned third controllable switch with short
pulses. In this case also the electricity supply to both the aforementioned windings
occurs via the same intermediate circuit of the brake control circuit, which simplifies
the construction of the brake control circuit.
[0025] In one embodiment a fourth controllable switch is fitted to the brake control circuit,
and the electricity supply from the intermediate circuit to the winding of the first
brake is arranged to be disconnected by opening the second controllable switch, and
the electricity supply from the intermediate circuit to the winding of the second
brake is arranged to be disconnected by opening the fourth controllable switch.
[0026] In one embodiment the brake control circuit is arranged to close at first only the
first brake in connection with an emergency stop, and the brake control circuit is
arranged to close also the second brake, if the movement of the elevator car determined
by the movement control system during an emergency stop decelerates by less than the
minimum deceleration during an emergency stop according to the reference set for movement.
In this case the braking force of the elevator machine and thus the deceleration of
the elevator car can be increased e.g. in steps, so that the braking force increases
to be greater the more the machinery brake closes to brake the movement of the elevator
machine.
[0027] In the following, the invention will be described in more detail by the aid of some
examples of its embodiments, which in themselves do not limit the scope of application
of the invention, with reference to the attached drawings, wherein
- Fig. 1
- presents one elevator system working according to the invention
- Fig. 2
- presents one brake control circuit working according to the invention
- Figs. 3a - 3d
- present some emergency stop situations
- Figs. 4a, 4b
- present the operation of a movement control system working according to the invention
- Fig. 5
- presents a brake working according to the invention,
- Fig. 6
- presents the monitoring of the movement of the elevator car during an emergency stop.
[0028] In the elevator system of Fig. 1, the elevator car 15 and the counterweight 28 are
supported with elevator ropes passing via the traction sheave 20 of the elevator machine
17. The traction sheave is integrated into the rotor of the elevator machine. A communication
connection is arranged between the different control units of the elevator system.
The structure of this type of serial mode communications channel is prior art in its
basic principles, and it is not presented here in more detail. It should be noted,
however, that the communication of the electronic monitoring unit 13 that monitors
the safety of the elevator system with the sensors that measure the safety of the
elevator system and the actuators that perform the procedures that ensure the safety
of the elevator system occur redundantly such that the electronic monitoring unit
13 both sends and receives, either along parallel data buses simultaneously or along
the same data bus consecutively, two separate data that determine the same safety
function of the elevator system. In this case the electronic monitoring unit 13 e.g.
receives movement data 18 of the elevator car via two channels from an acceleration
sensor fixed in connection with the elevator car, from an encoder connected to a rotating
part 20 of the hoisting machine 17, or from a signal of both the acceleration sensor
and the encoder; in the lattermost case it is sufficient to satisfy the two-channel
requirement that only a singe-channel movement signal is generated from both movement
data. If the separate movement signals 18 that are using two channels determine the
same movement data referred to above differ from each other by more than the set limit
value, the electronic monitoring unit 13 deduces that at least one measurement of
movement data is malfunctioning and thus determines an operational nonconformance
of the movement control system 14 of the elevator system. The electronic monitoring
unit as well as the sensors and actuators connected to the safety of the elevator
system in this case form the safety circuit of the elevator.
[0029] The power supply of the permanent-magnet synchronous motor 17 that moves the elevator
car 15 occurs from the electricity network 28 with a motor control unit 19, with which
a rotating current vector that moves the rotor is formed in a way that is, in itself,
prior art. The movement control system 14 measures the speed 18 of the traction sheave
of the elevator motor with an encoder. The current to be supplied to the elevator
motor 17 is adjusted with the frequency converter such that the measured speed of
the traction sheave 20, and thus also the speed of the elevator car, adjusts to correspond
to the reference for speed. The aforementioned reference for speed is updated as a
function of the position of the elevator car 15 moving in the elevator hoistway.
[0030] Two electromechanical brakes 2, 2', which both connect to the braking surface of
a rotating part to prevent movement of the traction sheave 20, are fitted in connection
with a rotating part of the elevator machine 17. Control of the brake occurs by supplying
brake current to the excitation winding 3, 3' of both brakes with a brake control
circuit 1. The brake control circuit comprises a first switch that controls the electricity
supply of the winding of the brake, which switch is switched in a controlled manner
with short pulses by the control of the electricity supply of the winding of the brake,
and thus the braking function is controlled.
[0031] As mentioned above, the electronic monitoring unit 13 measures the state of the sensors
that monitor the safety of the elevator system and deduces any operational nonconformance
of the elevator system. On the basis of an operational nonconformance of the elevator
system, the safety circuit of the elevator can perform an emergency stop. In this
case, if e.g. the contact that measures the position of a landing door detects opening
of the landing door during an elevator run, the electronic monitoring unit 13 initiates
an emergency stop. An emergency stop can often be initiated also manually, e.g. by
using an emergency stop button fitted into the elevator car, the status of which is
read by the monitoring unit 13. The electronic monitoring unit 13 determines the operating
condition of the movement control system 14 in connection with an emergency stop by
comparing two movement signals that determine the movement of the elevator car, and
that are generated with a different sensor, with each other in the manner described
above. If the movement signals correspond to each other with sufficient accuracy,
the monitoring unit 13 further compares one of the movement signals to the limit values
set for permitted movement of the elevator car; if the movement is in this case in
the permitted range set by the limit values, the monitoring unit 13 deduces that the
movement control system 14 is in working order. Conversely, if the movement signals
18 in this case differ from each other by more than the limit value, or if the movement
of the elevator car deviates to outside the range of permitted movement set by the
limit values, the monitoring unit deduces an operational nonconformance of the movement
control system 14.
[0032] When executing an emergency stop the monitoring unit 13 also disconnects the electricity
supply of the elevator motor 17 by controlling open at least the switches of the motor
bridge of the frequency converter as well as also any contactor or corresponding contacts
possibly disposed between the electricity network 29 and the motor control unit 19.
[0033] When it detects an operational nonconformance of the movement control system 14,
the electronic monitoring unit 13 sends to the brake control circuit 1 a control command,
on the basis of which the brake control circuit 1 disconnects the electricity supply
to the windings 3, 3' of the brake completely as soon as possible. In this case also
the machinery brakes 2, 2' engage with a moving part of the machine with as great
a force as possible, and the elevator car stops with maximum deceleration. In this
case the deceleration during an emergency stop can be e.g. approx. 0.66G. The electricity
supply to the windings 3, 3' of the brake can be disconnected in a corresponding manner
also, e.g. in connection with an electrical power outage of the elevator system.
[0034] When it detects that the movement control system 14 is in working order, the electronic
monitoring unit 13 sends to the brake control circuit 1 a control command, on the
basis of the supply of electricity to the winding of the brake is permitted also in
connection with an emergency stop. In this case the movement control system 14 adjusts
by means of the brake control circuit 1 the speed 18 of the elevator car 15 towards
the speed reference to be used during an emergency stop so that the elevator car stops
in a controlled manner with the deceleration set by the speed reference. The value
of deceleration can in this case vary, according to the operating circumstances and
the deceleration stage, and it can be e.g. approx. 0.33G.
[0035] Fig. 2 presents the main circuit of one brake control circuit 1 working according
to the invention. Also the main circuit of the brake control circuit dealt with in
Fig. 1 can be this type; on the other hand, the brake control circuit 1 to be presented
is also suited to elevator systems in which a conventional safety circuit is used
in the safety circuit of the elevator instead of an electronic control unit 13. In
this case the electricity supply to the brake control circuit 1 is fitted to be disconnected
with a normally open contact, the control of which disconnects the safety circuit
when it opens.
[0036] A first controllable switch 4 is fitted in series with the winding 3 of the first
brake, which switch is switched with short pulses when controlling the electricity
supply of the first brake 2. The first controllable switch can be implemented with
e.g. an IGBT transistor, a MOSFET transistor or with another solid-state switch. The
switching frequency of the first switch is essentially greater than the frequency
of the AC voltage source supplied to the brake control circuit 1, usually by at least
several kilohertz. A second controllable switch 12, which when controlling the brake
is kept continuously closed at the same time as the first controllable switch 4 is
switched, is further fitted in series with the winding of the first brake. The intermediate
circuit 5 is made by rectifying the voltage of the AC voltage source with a diode
rectifier 21. Another network commutating rectifier can also be used instead of a
diode rectifier, in which case the diodes of at least the upper or the lower branch
can be replaced with e.g. thyristors. The intermediate circuit can also be formed
to be regulated by using e.g. some prior-art DC/DC transformer or AC/DC transformer;
the brake control circuit 1 can also comprise a transformer, with which the winding
of the brake is galvanically isolated from the AC voltage source. A capacitor 10 is
connected between the rails 5, 5' that transfer output current and return current
to the intermediate circuit of the brake control circuit 1. By means of the capacitor
the fluctuations in voltage produced by the diode rectifier 21 can be compensated.
A capacitor 10 can be connected and isolated from the intermediate circuit with a
switch fitted in series with the capacitor.
[0037] The electricity supply of the winding 3 of the brake can be disconnected by opening
the second controllable switch 12. When in addition the first controllable switch
4 is opened, the current flowing in the winding, and thus the energy stored in the
winding, starts to discharge via the diodes 6, 7 forming the release branch of the
intermediate circuit 5 of the brake control circuit. The interference produced by
commutation can be reduced by opening the first controllable switch 4 before the second
controllable switch 12 is opened. After the switches have opened, the magnetization
energy discharged from the winding 3 of the brake starts to be stored in the intermediate
circuit capacitor 10, and the voltage of the capacitor starts to increase. After the
voltage has increased sufficiently, the varistor 8 or corresponding fitted in parallel
with the winding switches to be conductive via the diode 9. The varistor then starts
to discharge the energy of the winding as heat, limiting at the same time the increase
in intermediate circuit voltage. Since only a part of the energy of the winding changes
in this case to heat in the attenuation circuit formed by the varistor 8 and the diode
9, and the rest of the energy is stored in the intermediate circuit capacitor 10,
the dimensioning of the attenuation circuit 8, 9 can be reduced.
[0038] A third controllable switch 4' and also a fourth controllable switch 12' are fitted
in series with the second winding 3' of the brake. The operation of the third controllable
switch 4' is in this case similar to that of the first controllable switch 4, and
likewise the operation of the fourth controllable switch 12' corresponds to the operation
of the second controllable switch 12. Discharge of the energy of the winding 3' of
the second brake also occurs via the second release branch 6', 7' in a corresponding
manner as in the case of the first winding, so that the operation of their main circuit
parts are not separately described here. What must be noted instead, however, is that
in this case the electricity supply to the windings of both the first and of the second
brake occurs from the same intermediate circuit; also both the first 6, 7 and the
second 6', 7' release branch discharge energy into the same intermediate circuit,
in which case the construction of the main circuit of the brake control circuit is
simplified.
[0039] Figs. 3a - 3d present some emergency stop situations of an elevator, by means of
which e.g. the operation of the brake control circuit of Fig. 2 is illustrated. Here,
for the sake of clarity and to simplify the description, the machine of the elevator
is braked with only one brake, the electricity supply of the winding of which brake
is controlled. It is, however, possible that the machine of the elevator comprises
at least two brakes, in which case the current supply to the windings of both of them
is controlled; in this case the currents of the windings can be essentially of equal
magnitude, but they can also if necessary be selected to differ from each other, particularly
if the constructions of the brakes in this case differ from each other. The construction
of the brake used is in its basic principle of the type presented in Fig. 5. Fig.
3a presents a graph of the current of the winding 3 of the brake of an elevator in
a situation in which the current supply to the winding is disconnected by opening
the first 4 and the second 12 controllable switch. At the moment in time 31 the switches
open, at the moment 32 the current 11 of the winding 3 of the brake has decreased
so much that the pushing force exerted by the helical springs 24, 24' on the brake
shoe 25' exceeds the attraction force produced by the current flowing in the winding
3 of the brake, in which case the brake shoe 25' starts to move towards the braking
surface 26; at the moment 33 the brake has closed, and in this case the brake pad
27 engages against the braking surface 26. After this the current goes to zero at
the speed determined by the attenuation circuit and/or the release circuit, depending
on the amount of magnetization energy committed to the winding. Fig. 3b presents the
speed 18 and the deceleration 18' of an elevator car when the brake 2 is controlled
in the manner presented in Fig. 3a. Since the current of the winding of the brake
in this case decreases rapidly to zero, the brake pad engages to brake with its maximum
force, in which case also the deceleration is great, preferably approx. 0.6...0.66G,
and the elevator car stops quickly with a short braking distance.
[0040] Fig. 3c presents the speed and deceleration of the elevator car in a situation in
which the movement control system is verified as being in working order, and the brake
is controlled by adjusting the current of the winding of the brake during an emergency
stop by connecting with short pulses the first controllable switch 4, such as is explained
in conjunction with the embodiments of Figs. 1 and 2. In this case the movement control
system 14 adjusts by means of the brake control circuit 1 the speed 18 of the elevator
car 15 towards the speed reference used during an emergency stop so that the elevator
car stops in a controlled manner with the deceleration set by the speed reference.
The value of deceleration is here approx 0.33G. Fig. 3d, on the other hand, presents
a reference 11 for current in connection with an emergency stop according to Fig.
3c, in which case the current reference varies as a response to the adjustment magnitudes
of the movement of the elevator car.
[0041] Figs. 4a, 4b present in more detail one possible movement control system 14. For
example, in an elevator system according to the embodiment of Fig. 1, one or more
of the electronic safety devices presented here can be used, if necessary. According
to Fig. 4a, a redundant serial communication bus 34 is fitted between the movement
control system 14, the electronic monitoring unit 13, the monitoring unit 35 of the
movement of the elevator car and the brake control circuit 1, via which bus the devices
communicate between themselves using duplicated communication. The movement signals
18 that determine the movement of the elevator car are also transferred by two channels
via the serial communication bus 34, in which case the movement signals can be read
by one or more devices connected to the serial communication bus 34.
[0042] The brake control circuit 1 comprises a structurally duplicated redundant control
14', which is made from prior-art electronic safety devices complying with the required
design criteria. The control 14' is made here with two microcontrollers that monitor
the operation of each other, in which case a failure of one or other microcontroller
is detected immediately.
[0043] The condition of the movement control system 14 is monitored on the basis of the
movement signals of the elevator car, as is described above e.g. in the embodiment
of Fig. 1. The monitoring of condition can be performed e.g. with an electronic monitoring
unit 13 or with the monitoring unit 35 of the movement of the elevator car, which
is also designed to be an electronic safety device. If on the basis of the movement
signals 18 of the elevator car the movement control system 14 is detected to be in
working order in connection with an emergency stop, the supply of current to the winding
3 of the brake is permitted, and the elevator car is stopped during an emergency stop
in a controlled manner with a deceleration ramp by adjusting the current of the brake,
using e.g. a deceleration of the magnitude of e.g. approx. 0.33G. The redundant control
14' of the brake control circuit manages the adjustment of the movement of the elevator
car as well as also the adjustment of the current of the winding 3 of the brake during
an emergency stop, which redundant control thus also comprises certain functions of
the movement control system. Fig. 4b presents in more detail the operation of the
redundant control 14' of the brake control circuit during an emergency stop. The control
14' receives from the serial communication bus 34 the movement signals 18 of the elevator
car generated by two different measuring apparatuses so that the first microcontroller
receives the movement signal of the first measuring apparatus and the second microcontroller
receives the corresponding movement signal of the second measuring apparatus. After
this the control 14' compares the movement signals with each other to ensure their
correctness. If the signals differ from each other by more than the set limit value,
the control 14' disconnects the current supply of the winding 3 of the brake by opening
the first 4 and the second 12 controllable switch. Conversely, if the movement signals
correspond to each other with sufficient accuracy, the redundant control 14' of the
brake control circuit compares at least one of the movement signals to the limit value
for permitted movement of the elevator car, such as e.g. to the limit value curve
of the maximum permitted speed during an emergency stop, to the limit value curve
of the minimum permitted deceleration during an emergency stop, and/or to the limit
values that determine the permitted position of the elevator car in the elevator hoistway.
If the movement of the elevator car in this case differs from what is permitted, the
control 14' disconnects the current supply of the winding 3 of the brake by opening
the first 4 and the second 12 controllable switch. It is also possible that a separate
safety device, such as an electronic monitoring unit 13 or a monitoring unit 35 of
the movement of the elevator car, manages the monitoring of the operating condition
of the measuring signals of the movement of the elevator car and/or of the movement
of the elevator car during an emergency stop. In this case the redundant control 14'
of the brake control circuit can also receive a measuring signal 18 of the movement
of the elevator car just on a single channel.
[0044] The redundant control 14' of the brake control circuit either generates a reference
16 for the movement of the elevator car during an emergency stop or one is already
stored in the memory of the control. The regulator 36 of the movement of the elevator
car forms a reference for the current of the brake in response to the difference between
the reference for the movement of the elevator car and the measured movement signal
of the elevator car. The control of the electricity supply of the winding of the brake
adjusts the current of the winding of the brake towards the current reference formed
with the current regulator 37, in which case the movement of the elevator car adjusts
towards the reference for movement during an emergency stop. The control of the electricity
supply of the winding of the brake also controls the controllable switch 4 of the
brake control circuit with a switching reference, which is formed with a pulse-width
modulator 39.
[0045] Fig. 5 presents a schematic diagram of a brake 2 working according to the invention.
The electromechanical brake 2 comprises a magnetic circuit, which comprises at least
two ferromagnetic parts 25, 25' fitted to move in relation to each other. Of the parts,
the first 25 is fixed to a stationary part (not in figure) of the elevator machine,
and the second part 25', i.e. the brake shoe, is attached to the brake pad 27, which
is fitted to connect to the braking surface 26. In this case a thrusting force is
exerted between the ferromagnetic parts 25, 25' via two helical springs 24, 24', which
thrusting force presses the brake pad 27 to the braking surface 26. An excitation
winding 3 is wound around the first part 25 of the ferromagnetic core of the magnetic
circuit of the brake 2. The current supply to the excitation winding 3 produces a
force of attraction between the ferromagnetic parts 25, 25', in which case when the
current and at the same time the force of attraction progressively increase, the second
part 25' of the magnetic circuit finally starts to move towards the first part 25,
pulling at the same time the brake pad 27 away from the braking surface 26. The air
gap 28 of the magnetic circuit between the first 25 and the second 25' part starts
to decrease, and finally goes to zero when the magnetic circuit closes. At the same
time the brake opens, and the traction sheave can rotate. Correspondingly, when the
current of the excitation winding 3 progressively decreases, the second part 25' of
the magnetic circuit finally starts to move away from the first part 25, pressing
at the same time the brake pad 27 against the braking surface 26. In this case the
brake engages to prevent movement of the traction sheave. Since the force exerted
on the brake pad 27 by the helical springs 24, 24' can be reduced by supplying current
to the excitation winding 3, the braking force can thus also be reduced with the current
control of the brake e.g. in connection with an emergency stop of the elevator.
[0046] The adjustment during an emergency stop of the movement of the elevator car by adjusting
the braking force of the machinery brake presented as an embodiment of the invention
also requires that the condition of the machinery brakes are monitored and that the
brakes are verified as being in operating condition before starting the adjustment.
A number of methods are presented in prior art for monitoring the condition of a brake,
and they will not be examined in more detail here.
[0047] Fig. 6 presents the monitoring of the movement of the elevator car during an emergency
stop. The monitoring of movement presented in the embodiments described above can
be implemented, but it is not necessarily implemented in the way presented here. According
to Fig. 6, a first limit value curve 40 is determined for the maximum speed of the
elevator car during an emergency stop, to which the measured speed 18 of the elevator
car is compared. If the measured speed 18 exceeds the first limit value curve 40 of
permitted speed, the electricity supply to the winding of the brake is disconnected
as quickly as possible. If the speed of the elevator car nevertheless continues to
increase, exceeding the second limit value curve 41, after the current of the winding
of the brake has been disconnected, the safety gear of the elevator car is also controlled.
The aforementioned second limit value curve 41 is determined for larger speeds than
the first limit value curve 40 throughout its definition range so that the first 40
and the second 41 limit value curve of speed never cross each other.
[0048] Also a first limit value curve 40' is determined for the minimum permitted deceleration
of the elevator car in Fig. 6, to which the measured deceleration 18' of the elevator
car is compared. If the measured deceleration falls below the first limit value curve
40' of permitted deceleration, the electricity supply to the winding of the brake
is disconnected as quickly as possible. If the deceleration of the elevator car nevertheless
continues to decrease, falling below the second limit value curve 41', after the current
of the winding of the brake has been disconnected, the safety gear of the elevator
car is also controlled. The aforementioned second limit value curve 41' is determined
for smaller decelerations than the first limit value curve 40' throughout its definition
range so that the first 40' and the second 41' limit value curve of deceleration never
cross each other.
[0049] Monitoring of the movement of the elevator car during an emergency stop can also
be implemented by monitoring just the speed of the elevator car or the deceleration
of the elevator car in the manner described above.
[0050] The aforementioned limit value curves 40, 40', 41, 41' of deceleration and/or of
speed of the elevator car during an emergency stop are here determined as a function
of time, but they can also be determined as a function of e.g. the position of the
elevator car in the elevator hoistway; and particularly in that way if the elevator
car is situated in the end zone of the elevator hoistway during an emergency stop.
[0051] It is obvious to the person skilled in the art that different embodiments of the
invention are not limited to the example described above, but that they may be varied
within the scope of the claims presented below.
[0052] It is also obvious to the skilled person that the solution according to the invention
can be applied in an elevator system with counterweight as well as in an elevator
system without counterweight.
[0053] It is obvious to the person skilled in the art that the structure of a brake presented
in Fig. 5 is only an example, and that the effect of the invention can be achieved
with many different structures.
[0054] It is further obvious to a person skilled in the art that one or more of the aforementioned
electronic devices can also be integrated together e.g. onto the same circuit card
/ into the same control unit.
1. Verfahren zum Steuern der einer Bremsfunktion einer Bremse eines Aufzugs mittels eines
Bremssteuerkreises (1), aufweisend einen ersten Schalter (4), der die Stromversorgung
einer Wicklung (3) der Bremse steuert, wobei der Schalter in einer gesteuerten Weise
mit kurzen Pulsen durch eine Steuerung (37, 39) der Stromversorgung der Wicklung der
Bremse geschaltet wird, wobei, nachdem die Stromversorgung der Wicklung (3) der Bremse
durch Öffnen eines zweiten steuerbaren Schalters unterbrochen wurde, die in der Wicklung
gespeicherte Energie in einen Zwischenkreis (5) des Brems-Steuerkreises über einen
Freigabezweig (6, 7) entladen wird, um die in der Wicklung der Bremse gespeicherte
Magnetisierungsenergie mittels eines Kondensators zu sammeln, der zwischen den Anschluss-Leisten
angeschlossen ist, die den Ausgangsstrom übertragen und Strom an den Zwischenkreis
zurückführen, so dass die gespeicherte Energie dann auch als Magnetisierungsenergie
der Bremswicklung wiederverwendet werden kann.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass wenn die Spannung des Zwischenkreises (5) einen gesetzten Grenzwert überschreitet,
Energie in einen Dämpfungskreis (8, 9) abgeleitet wird, der parallel zur Wicklung
der Bremse vorgesehen ist.
3. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der Strom der Bremse in Richtung der gesetzten Referenz (11) für den Bremsstrom eingestellt
wird, indem der erste steuerbare Schalter (4) mit kurzen Pulsen geschaltet wird.
4. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der erste steuerbare Schalter (4), der mit kurzen Pulsen geschaltet wird, in Reihe
mit der Wicklung der Bremse geschaltet ist; und dass ein zweiter steuerbarer Schalter
(12), der beim Steuern der Bremse zeitgleich kontinuierlich geschlossen gehalten wird,
wenn der erste steuerbare Schalter (4) mit kurzen Pulsen geschaltet wird, ferner mit
der Wicklung der Bremse in Reihe geschaltet ist;
und dass die Stromversorgung vom Zwischenkreis (5) zur Wicklung (3) der Bremse durch
Öffnen des zweiten steuerbaren Schalters (12) abschaltbar angeordnet ist.
5. Verfahren nach vorstehendem Anspruch 4, dadurch gekennzeichnet, dass der erste (4) und zweite (12) Schalter so angeordnet sind, dass sie auf der Grundlage
von Zustandsdaten eines Sicherheitskreises (13) des Aufzugs gesteuert werden.
6. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass bei der Erkennung eines Leitungs-zu-Erde-Kurzschluss der Bremse nur der erste Schalter
(4) geschlossen wird, und dass der Leitungs-zu-Erde-Kurzschluss in diesem Fall auf
der Grundlage des durch den ersten Schalter fließenden Stroms bestimmt wird.